238 lines
11 KiB
Plaintext
238 lines
11 KiB
Plaintext
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==)--- P TO PAUSE S TO STOP ---(==
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\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`
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Basic Signaling, PT I
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{C} 1987 Asmodeus Rex OOTR/cDc
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Transcribed From 1986 Bell Tech
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\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`
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This is the start of a sequence of info that someof you may or may now know..
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if you know it all, tell me and i will resort to something else..
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Basic Signaling
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4.1 General
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Signaling is the means used to establish and control telephone
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calls. It includes signals from terminals (station signaling), to and from
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switching centers (register signaling), and also signals between switching
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centers (line signaling). Signals are carried by the line and trunk
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transmission equipment and the switching system which convay information and
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commands to and from the various parts of the system and operating
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administration signals.
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The modes of signaling which will be summarized include the following
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types..
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4.1.1 Direct Current Signaling
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In the direct current signaling method (loop-disconnect signaling), a
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signaling code is derived from the duration and direction of the current
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flowing through a loop. This loop includes the customer's telephone and the
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line transmission equipment and it's switching center interface. Direce
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current loop signaling is also used with trunk transmission equipment of the
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wire type.
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An alternative methd of direct current signaling uses only one of the
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pair of wires and is called leg signaling
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4.1.2 Alternating Current Signaling
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Alternating current signaling is based on signals of different
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frequency either in the same bandwidth (in band) as the speech transmission
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path (300 to 3400 Hz) or at a lower, <300 Hz, or at a higher, >3400 Hz,
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frequency (out band).
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4.1.3 Digital Signals
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Digital signals take the form of a series of successive pulses, binary
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signals, which are coded to produce a signaling format. Digital signals may
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occupy a portion of one of the time slots used for the transmission of speech
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(in slot) or may used a dedicated time slot (our slot).
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4.1.4 Signaling Path
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Signaling may use the same transmission path as the speech or datd
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signals or it may use a seperate channel. The first case is called Channel
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Associated Signaling, the second case Common Channel Signaling.
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Common Channel Signaling. Shows the principle of operating for common
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channel signaling. The signalin function for both line and register signaling
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is removed from the path carrying the transmission signals. In lieu of this a
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series of messages indicating the originating and terminating trunk
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identities, together with the relevant address or line signals, is sent over a
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seperate dedicated channel. This information is processed in the system
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controls at either end and decoded to produce the relevant actions. There are
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two such systems in use, or planned for use: CCITT System #6, which uses an
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analog signaling in band method by the use of data modems, and CCITT System
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#7, which uses pulse code modulation (PCM) coded signals operating at 64,000
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BPS.
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\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\
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Basic Signaling Pt II
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{C} 1987 Asmodeus Rex - cDc
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OOTR/PAWW/MBI/MCI
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Transcribed From 1986 Bell
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\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\
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This File Was First Left On P-80, All Credit Of This File Must Be Left to
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P-80 When Posted On Other Systems.. - Rexxy
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4.1.5 Signalin over a Carrier System
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The signaling path may consist of wire conductors or it may be derived
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from a carrier system. This provides a dedicated derived channgd from one of
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the 'n' inputs to one of the 'n' outputs. It uses either frequency
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multiplexing or pulse code modulation to multiplex the channels.
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4.1.5.1 Frequency Division Carrier
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In the case of frequency division a number of channels are each
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allocated a por4ion of the bandwidth of the carrier system. Each portion is
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multiplexed with the carrier frequency by thE multiplexing equipment at the
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send end. It is demultiplexed and filtered to select the relevant channel at
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the recieve end to restore the speech wave form.
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4.1.5.2 Pulse Code Modulation Carrier
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In the case of pulse code modulation a number of channels are each
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allocated a time slot which has a fixed recurring position in a frame of time
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slots. The analog input to each channel is sampled and coded at the send side
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and interleaved with the other time slots by the multiplexing equip. The
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channel is extracted at the receive en$ and demultiplexed back to analog.
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Signaling systems are designed for the various transmission modes and
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means.
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4.2 Station Signaling
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Station signaling controls the transmission path between the terminal
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and the exchange and provides address information. It is used for the duration
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of th call. Address signaling is used to set the call up and to initiate
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certain kinds of services, some of which are described later on..
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4.2.1 Signals From Telephone
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Present-day telephones have the following signaling elements.
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o A hook switch which completes the loop circut when the telephone
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handset is lifted. This is used to originate or answer a call.
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Replacement of the handset opens the loop and terminates the call.
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o A calling device, which is either a rotary dial or a key pad. to
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produce the address signals, henceforth the station signals
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address information to the switching system center register
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using either dial pulses or DTMF pulses.
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o An alerting device, usually a bell, to indicate a call terminating
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on the line.
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4.2.1.1 Rotary Dial
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The calling device which is in most common us% as The rotary dial. The
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rotary dial produces dial pulse (loop disconnect) signals.
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This calling arangement uses the standard telephone dial. rotary type,
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usuallt having a pulsating rate of 10 impulses per second. (IPS). However, 20
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IPS dials are used in certain countrys. Dial pulsing utilizes a train of one
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to 10 pulses, each pulse consisting of a momentary opening of the signaling
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loop. The digit to be dialed is selected by rotating the dial manualy to the #
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selected and releasing the dial produces a requisite pulse train.
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The loop disconnect signals in general use, these include switch hook
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or equivalant signals.
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4.2.1.2 Loop-Disconnect Station Signaling
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A calling line originates a call by a request for service signal which
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)s produced when the telephone handset is removed. This signal is detected by
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the line circut which associates a callin' device detector and a register.
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Dial tone is returned to the caller, who then dials the address of the
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requested party. The register stores the dialed units and hence accumulates
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the address information. The line circut register and calling device deteator
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respond to the following loop-disconnect signals.
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'Closed Loop Signals' These can indicate a request for service or the
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end of a train of digits. IN the first use the signal must persist for a
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minimum of 10Msec. A signal occuring after request for service must persist
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for a minimum of 180Msec. duration to be recognized as the end of a series of
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pulses corresponding to a digit. (Interdigit Signal).
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If the signal occurs after all digits have been recieved then it is a
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control signal.
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'Open Loop Signals' An open-loop signal can either be the beginning of
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a dial pulse or at the beginning of a disconnect or 'hook-switch flash'
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signal. If the signal is the begining of a dial pulse it will be followed by a
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closed loop condition within 180 Msec. If the signal is the beginning of a
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"hook switch flash" it will be follwed by a closed loop condition within 1 or
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2 seconds. Services using "hook-switch flash" are those services which require
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the connection of functional units to an established call without
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disconnecting the established connection. Hence, depending on the class of
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service of the caller, a sustained open-loop condition which occurs after a
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closed loop must last longer than 180 Msec or 2 Sec to be recognized as a
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disconnect signal..
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\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`
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Basic Signaling - Pt III
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{C} 1987 Asmodeus Rex - cDc/OOTR
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AEUA/MCI/MBI/PAWW
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Transcribed From 1986 Bell
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\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`
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4.2.1.3 Tone Signaling from Station
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The advent of low-cost electronic components has made the use of
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key-controlled oscillators as calling devices feasible. The generic term is
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'Dual Tone Multi Frequency' (DTMF). This calling device has push-button keys
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on the telephone innstruments which transmit two frequencies when one key is
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pressed. Signals are those developed by the 'Bell System' for tuch-tone
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service, which is a registerd trademark of Western Electric Co.
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Key plates in normal use have only 10 or 12 of the 16 possible keys,
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but some systems should be capable of responding to all 16 codes for future
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applications.
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4.2.1.4
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Registers serving lines are designed to respond to either dial pulses
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or DTMF signals. This uses serarate process for dial pulse and DTMF but the
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resulting digit (whether it was determined by counting pulses or decoding
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voice frequency signals) is coded in the system code (usually binary-coded
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decimal) and stored.
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4.2.1.5 Binary Coded Decimal
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This coding method uses for bits per decimal digit. The first ten of
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the 15 possible combinations are used. The four bits have the most significant
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bit value (eight) on the left hand side and numbers are coded by summing the
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bit values; EX: Decimal value 1 is coded as 0001 and decimal value 10 is coded
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1010. This method, which separately codes each decimal digit, has advantages
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in analyzing the digits dialed by th caller and relating them to the numbering
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plan.
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4.2.2 Signals To Telephones
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The signals to the telephone of the calling party consist of tone
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signals, or messages, to the caller. These direct the caller's actions or
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advise him or her of the progress of the call. The frequencies and cadences if
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these tones may vary from country to country, but the CCITT is recommending
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the use of standard tones. This has become increasingly important with the
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introduction of direct international dialing. Inaddition to this there are
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signals which alert a caller customer. Another signal informs a customer that
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the telephone handset has been left of the hook, without dialing, for a
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predertimed period.
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Call These BBS's
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[The Alcazar Elite..............................................401/789-0094]
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[Sanctuary North Private........................................507/288-9572]
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Downloaded from P-80 Systems.....
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Originally Displayed on P-80 Systems.
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